Flying Bat-Inspired Robots May Take to the Skies

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The way bats rapidly flap their wings in flight could inspire new
designs of flying robots, according to a new study.

Researchers studied how fruit bats use their wings to manipulate
the air around them. Understanding how these processes work in
nature could help engineers design
small flying robots, known as "micro air vehicles," with
flapping wings, the scientists said.

"Bats have different wing shapes and sizes, depending on their
evolutionary function," Danesh Tafti, a professor in the
department of mechanical engineering and director of the High
Performance Computational Fluid Thermal Science and Engineering
Lab at Virginia Tech, said in a statement. "Typically, bats are
very agile and can change their flight path very quickly —
showing high maneuverability for midflight prey capture, so it's
of interest to know how they do this." [ The
6 Strangest Robots Ever Created ]

Fruit bats, and more than 1,000 other species of bats, have wings
made of flexible, "webbed" membranes that connect their fingers,
the researchers said. Fruit bats typically weigh about an ounce
(30 grams), and their fully extended wings can each measure
roughly 6.7 inches (17 centimeters) in length, Tafti said.

To examine how these creatures flap their wings, the scientists
collected measurements of live flying bats and used specially
designed software to analyze the relationship between the
animals' movements and the motion of airflow around their wings.

They found, surprisingly, that bats could
change the movement of their wings in order to maximize the
forces generated by the flapping. This means a bat can increase
the area of its wing by as much as 30 percent to maximize
favorable forces as it pushes downward. Conversely, a bat can
decrease the area of its wing by a similar amount as it flaps
upward, which helps minimize unfavorable forces pushing down and
keeps the bat agile midflight.

"Next, we'd like to explore deconstructing the seemingly complex
motion of the bat wing into simpler motions, which is necessary
to make a bat-inspired flying robot," study co-author Kamal
Viswanath, a research engineer at the Laboratories for
Computational Physics and Fluid Dynamics at the U.S. Naval
Research Lab in Washington, D.C., said in a statement.

The researchers also hope to examine how different wing motions,
not just surface area, affect the force produced by the flying
bat.

"We'd also like to explore other bat wing motions, such as a bat
in level flight or a bat trying to maneuver quickly to answer
questions, including: What are the differences in wing motion,
and how do they translate to air movement and forces that the bat
generates?" Tafti said. "And finally, how can we use this
knowledge to control the flight of an autonomous flying vehicle?"

The detailed findings were published online today (Feb. 18) in
the journal Physics of Fluids.